374 Miscellaneous Intelligence. 



one simple effect, and subject to one general law. — Phil. Mag. 

 lxii. 321. 



3. Thermo-electric Phenomenon with Iron. — Professor dimming 

 has remarked, that if in the compound piece of two wires used to 

 produce electro-magnetic effects by heating, one of the pieces be iron, 

 and they be heated by a spirit lamp, the deviation, in some cases, 

 gradually attains a maximum, then returns through zero, and at a red 

 heat assumes an opposite direction ; resembling in this respect the 

 deviations before observed with an alloy of antimony and bismuth. 

 These effects took place when iron was connected with silver, copper, 

 gold, zinc, and brass, but not with platina or lead, and has not been 

 observed in other cases where neither of the wires were iron. 



The table which we copied in our last Number of the relations of 

 the thermo-electric bodies should be corrected, by having galena put 

 above bismuth, and silver between zinc and ore of iridium and 

 osmium. — Ann. Phil., N. S. vi. 321. 



4. Dobereiner's Eudiometer. — Professor Dobereiner has suggested 

 the use of finely divided platina for the purpose of detecting minute 

 portions of oxygen in a gaseous mixture, in which hydrogen also is 

 present. Its effect is immediate ; the moment the substance rises 

 above the surface of the mercury in the tube containing the mixture, 

 the combination of the oxygen and hydrogen begins, and in a few 

 minutes is completed ; and, as Professor D. has stated, it seems capa- 

 ble of detecting the smallest quantity of oxygen. Its utility in the 

 analysis of atmospheric air, and compounds containing oxygen, is 

 obvious, provided no combination also takes place between the hy- 

 drogen in excess, and the nitrogen (or other gas) that may be present, 

 as does in fact happen, according to Dobereiner, when protoxide of 

 platinum is so employed. 



Messrs. Daniell and Children mixed 20 measures of atmospheric 

 air, with 37 measures of hydrogen gas, and passed up to the mixture a 

 small portion of the platina powder, procured by heating the ammonia 

 muriate to redness, and made into a ball with precipitated alumina. 

 The pellet was heated red by the blowpipe, immediately before it was 

 used, its size about that of a small pea. The absorption amounted 

 to 13 measures = 4.3 oxygen, being 0.1 of a measure more than 

 the quantity of oxygen in 20 measures of atmospheric air, which may 

 probably have ari§en from a slight impurity in the hydrogen, or from 

 some minute unperceived bubbles of air, entangled in the mercury. 



Another mixture of common air and hydrogen, in which the latter 

 was in considerable excess, was deprived of its oxygen by the pellets, 

 and when the absorption was complete, 3S measures of the residual 

 gas were taken, and a fresh pellet, heated to redness, immediately 

 before it was used, passed up. After standing about a quarter of an 

 hour, no absorption had taken place. The tube and the mercury 



